CN113067604A - NFC access control circuit and NFC device - Google Patents

NFC access control circuit and NFC device Download PDF

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Publication number
CN113067604A
CN113067604A CN202010001257.4A CN202010001257A CN113067604A CN 113067604 A CN113067604 A CN 113067604A CN 202010001257 A CN202010001257 A CN 202010001257A CN 113067604 A CN113067604 A CN 113067604A
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China
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nfc
pin
module
switch
electrically connected
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CN202010001257.4A
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CN113067604B (en
Inventor
陈柳章
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Shenzhen Excelsecu Data Technology Co Ltd
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Shenzhen Excelsecu Data Technology Co Ltd
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Priority to CN202010001257.4A priority Critical patent/CN113067604B/en
Priority to PCT/CN2020/131559 priority patent/WO2021135741A1/en
Publication of CN113067604A publication Critical patent/CN113067604A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/70—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes
    • H04B5/72—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes for local intradevice communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/70—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Near-Field Transmission Systems (AREA)

Abstract

The NFC access control circuit and the NFC device comprise NFC equipment, an NFC induction module, a switch module, an access module and a control module, when a user does not need to use the NFC device, the switch module does not have high-level input, so that the NFC induction module and the NFC equipment are disconnected, and the NFC read-write device cannot access the NFC device. When a user needs to use the NFC device, the control module can output a high-level signal to the switch module only by triggering the access module, and the NFC induction module and the NFC equipment are conducted, so that the NFC device can be accessed. In addition, after the user operation is completed and the NFC device leaves the NFC read-write device, the control module can not output a high-level signal to the switch module any more, so that the NFC induction module and the NFC equipment are disconnected, and the NFC equipment cannot be accessed. Therefore, the NFC access control circuit provided by the invention is extremely convenient to operate and has no potential safety hazard.

Description

NFC access control circuit and NFC device
Technical Field
The invention relates to the technical field of NFC (near field communication) communication, in particular to an NFC access control circuit and an NFC device.
Background
An NFC antenna in an existing NFC device is usually directly electrically connected to an NFC device, so that corresponding read-write operations can be performed as long as the NFC device and other NFC read-write devices are within a communication range. But the mode of NFC antenna and NFC equipment direct electrical connection can lead to the NFC device to visit by unauthorized NFC read write device easily, and the NFC device is carried out data read-write operation through NFC read write device by other people easily under the condition that the user is unwilling promptly, for example the electron cash card that the user carried, if other people put NFC read write device near the position that the user placed electron cash card, alright easily deduct user's balance under the condition that the user is unwilling. Therefore, the existing NFC device can be directly accessed by the NFC read-write device, and great potential safety hazards exist.
Disclosure of Invention
In view of the above drawbacks of the prior art, an object of the present invention is to provide an NFC access control circuit and an NFC apparatus, which are used to solve the problem that the existing NFC apparatus can be directly accessed by an NFC reader/writer and has a large potential safety hazard.
In a first aspect, the NFC access control circuit provided by the present invention is applied to an NFC device, and includes an NFC device, an NFC sensing module, a switch module, an access module, and a control module;
the NFC induction module is electrically connected with the switch module, and the switch module is electrically connected with the NFC equipment; the NFC induction module is also electrically connected with the access module, the access module is electrically connected with the control module, and the control module is electrically connected with the switch module;
the NFC induction module is used for generating induction current and outputting direct-current voltage when the NFC device approaches the NFC read-write device;
the access module is used for conducting the NFC induction module and the control module only in a trigger state so as to trigger the control module;
the control module is used for outputting a high-level signal to the switch module after being triggered so as to trigger the switch module;
the switch module is used for conducting the NFC induction module and the NFC equipment when being triggered, so that the NFC device can be accessed by an NFC read-write device.
Further, the NFC sensing module includes an NFC antenna and a conversion circuit, the NFC antenna is electrically connected to an ac input terminal of the conversion circuit, a dc output terminal of the conversion circuit is electrically connected to the access module, a power input terminal of the control module, and a power input terminal of the switch module, respectively, and the NFC antenna is also electrically connected to the switch module;
the NFC antenna is used for generating alternating current output when the NFC device approaches the NFC read-write device; the conversion circuit is used for converting alternating current output generated by the NFC antenna into direct current and outputting direct current voltage.
Still further, the conversion circuit comprises a rectification circuit and a voltage stabilizing circuit, the NFC antenna is electrically connected with an alternating current input end of the rectification circuit, a direct current output end of the rectification circuit is electrically connected with the voltage stabilizing circuit, and the voltage stabilizing circuit is electrically connected with the access module, a power supply input end of the control module and a power supply input end of the switch module;
the rectification circuit is used for rectifying alternating current output generated by the NFC antenna into direct current output; the voltage stabilizing circuit is used for limiting and stabilizing the direct current output voltage of the rectifying circuit;
the rectifying circuit comprises a first rectifying diode, a second rectifying diode, a third rectifying diode and a fourth rectifying diode;
the positive electrode of the first rectifying diode is electrically connected with the negative electrode of the third rectifying diode so as to be used as a first pin of the alternating current input end of the rectifying circuit;
the positive electrode of the second rectifying diode is electrically connected with the negative electrode of the fourth rectifying diode so as to be used as a second pin of the alternating current input end of the rectifying circuit;
the negative electrode of the first rectifying diode is electrically connected with the negative electrode of the second rectifying diode to be used as a first pin of the direct current output end of the rectifying circuit;
and the anode of the third rectifying diode is electrically connected with the anode of the second rectifying diode so as to be used as a second pin of the direct current output end of the rectifying circuit.
Furthermore, the voltage stabilizing circuit comprises a voltage stabilizing tube and a filter capacitor; the cathode of the voltage-stabilizing tube is electrically connected with the first pin of the filter capacitor, and the anode of the voltage-stabilizing tube is electrically connected with the second pin of the filter capacitor;
the voltage-stabilizing tube is used for limiting the direct-current output voltage of the rectifying circuit, and the filter capacitor is used for stabilizing the direct-current output voltage of the rectifying circuit.
Still further, the access module comprises an access key, and the access key is electrically connected with the NFC sensing module and the control module respectively;
and when the access key is in a pressed state, the NFC induction module and the control module are conducted to trigger the control module.
Further, the switch module comprises a radio frequency switch, and the radio frequency switch comprises a power input pin, a ground pin, a control pin, a first switch pin and a second switch pin;
a power supply input pin of the radio frequency switch is electrically connected with the NFC induction module, and a grounding pin is grounded so that the NFC induction module provides working voltage for the radio frequency switch;
a control pin of the radio frequency switch is electrically connected with the control module, a first switch pin of the radio frequency switch is electrically connected with the NFC induction module, and a second switch pin of the radio frequency switch is electrically connected with the NFC equipment;
the radio frequency switch is used for conducting electric connection between the first switch pin and the second switch pin when the control pin has high level input so as to conduct the NFC induction module and the NFC equipment.
Still further, the switch module further comprises a pull-down resistor, a first pin of the pull-down resistor is electrically connected with a control pin of the radio frequency switch, and a second pin of the pull-down resistor is grounded;
the pull-down resistor is used for disconnecting the electric connection between the first switch pin and the second switch pin when the NFC induction module just generates direct current output so as to disconnect the connection between the NFC induction module and the NFC equipment.
Further, the control module comprises a first analog switch, wherein the first analog switch comprises a power input pin, a ground pin, a control pin, a switch pin and an output pin;
a power supply input pin of the first analog switch is electrically connected with the NFC induction module, and a grounding pin is grounded so that the NFC induction module provides working voltage for the first analog switch;
a control pin of the first analog switch is electrically connected with the access module, a switch pin is electrically connected with a power input pin, and an output pin is electrically connected with the switch module;
the first analog switch is used for conducting a switch pin and an output pin when a high level input exists at a control pin, so that the first analog switch outputs a high level signal to the switch module.
Still further, the control module further comprises a second analog switch, wherein the second analog switch comprises a power input pin, a ground pin, a control pin, a switch pin and an output pin;
a power supply input pin of the second analog switch is electrically connected with the NFC induction module, and a grounding pin is grounded so that the NFC induction module provides working voltage for the second analog switch;
a control pin of the second analog switch is electrically connected with the access module, a switch pin is electrically connected with a power input pin, and an output pin is electrically connected with the control pin and the control pin of the first analog switch respectively;
the second analog switch is used for conducting a switch pin and an output pin when the control module is triggered and working voltage input exists, and outputting high-level signals to the control pin and the control pin of the first analog switch through the output pin simultaneously so as to keep conduction between the switch pin and the output pin of the second analog switch and keep conduction between the switch pin and the output pin of the first analog switch.
Furthermore, the NFC read-write control circuit further includes a power-off delay module, a first pin of the power-off delay module is electrically connected to the access module and the control module, and a second pin is grounded;
the power-off delay module is used for getting and storing power from the NFC induction module when the access module is triggered, and providing high-level input of preset time for the control module when the NFC induction module cannot output normal voltage.
Still further, the power-off delay module comprises a delay capacitor and a delay resistor;
the first pin of the delay capacitor is electrically connected with the first pin of the delay resistor to be used as the first pin of the power-off delay module;
and the second pin of the delay capacitor is electrically connected with the second pin of the delay resistor so as to be used as the second pin of the power-off delay module.
In a second aspect, the present invention provides an NFC device, including the NFC access control circuit according to the first aspect, where when the NFC device is close to an NFC reader, the NFC device is controlled by the NFC access control circuit to be accessible by the NFC reader.
Has the advantages that: the NFC access control circuit and the NFC device comprise NFC equipment, an NFC induction module, a switch module, an access module and a control module, when a user does not need to use the NFC device, the switch module does not have high-level input, so that the NFC induction module and the NFC equipment are disconnected, and the NFC read-write device cannot access the NFC device. When a user needs to use the NFC device, the control module can output a high-level signal to the switch module only by triggering the access module, and the NFC induction module and the NFC equipment are conducted, so that the NFC device can be accessed. In addition, after the user operation is completed and the NFC device leaves the NFC read-write device, the control module can not output a high-level signal to the switch module any more, so that the NFC induction module and the NFC equipment are disconnected, and the NFC equipment cannot be accessed. Therefore, the NFC access control circuit provided by the invention is extremely convenient to operate and has no potential safety hazard.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic circuit diagram of an NFC access control circuit according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of an NFC sensing module according to an embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a switching circuit in the NFC sensing module according to an embodiment of the present invention;
FIG. 4 is a circuit schematic of a switch module in an embodiment of the invention;
FIG. 5 is a schematic circuit diagram of a control module in an embodiment of the invention;
FIG. 6 is a schematic circuit diagram of a power down delay module according to an embodiment of the invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The existing NFC device can be directly accessed by the NFC read-write device, so that great potential safety hazards exist. In order to solve the technical problem, in the embodiment of the present invention, a switch module is disposed between the NFC sensing module and the NFC device, and an access module is disposed to control the switch module to be turned on or off. Therefore, when a user does not need to perform data reading and writing operations, the NFC sensing module and the NFC equipment are in an off state due to the fact that the switch module is located between the NFC sensing module and the NFC equipment, and even if the NFC reading and writing device is close to the NFC device at the moment, the NFC reading and writing device cannot access the NFC equipment. When a user needs to perform data read-write operation, the switch module is triggered only through the access module to conduct the NFC induction module and the NFC equipment, and therefore the data read-write operation can be performed.
For example, the embodiments of the present invention may be applied to the scenarios described below. In this scenario, when the user carries the electronic cash card to perform the fund transaction operation, the electronic cash card needs to be close to the NFC read-write device of the merchant, and the access module enables the electronic cash card to be accessed by the NFC read-write device, so that the fund transaction operation can be performed. When the user does not need to use the electronic cash card, even if other people approach the NFC read-write device to the electronic cash card, the other people cannot deduct the balance of the user and other operations because the user does not trigger the access module. Therefore, the electronic cash card applying the embodiment of the invention has no potential safety hazard.
It should be noted that the above application scenarios are only presented to facilitate understanding of the present invention, and the embodiments of the present invention are not limited in any way in this respect. Rather, embodiments of the present invention may be applied to any scenario where applicable.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, an NFC access control circuit according to an embodiment of the present invention is applied to an NFC apparatus, and the circuit includes an NFC device 10, an NFC sensing module 20, a switching module 30, an access module 40, and a control module 50.
The NFC sensing module 20 is electrically connected with the switch module 30, and the switch module 30 is electrically connected with the NFC device 10; the NFC sensing module 20 is further electrically connected to the access module 40, the access module 40 is electrically connected to the control module 50, and the control module 50 is electrically connected to the switch module 30.
Specifically, when the NFC device is close to the NFC reader, the NFC sensing module 20 is configured to generate an induced current and output a dc voltage, and if the NFC sensing module is directly electrically connected to the NFC device 10, the NFC reader can directly access the NFC device.
Therefore, as a modification, the present embodiment provides the switch module 30 between the NFC sensing module 20 and the NFC device 10, and provides an access module 40 for controlling the switch module 30 to be turned on or off. Specifically, the access module 40 is configured to conduct the NFC sensing module 20 and the control module 50 only when in a trigger state, so as to trigger the control module 50; the control module 50 is configured to output a high-level signal to the switch module 30 after being triggered, so as to trigger the switch module 30; the switch module 30 is configured to, when triggered, turn on the NFC sensing module 20 and the NFC device 10, so that the NFC apparatus can be accessed by an NFC reader.
Specifically, when the user does not need to use the NFC device, the NFC sensing module 20 and the NFC apparatus 10 are disconnected by the switch module 30, so that others cannot access the NFC device by using the NFC reader. When a user needs to use the NFC device, the access module 40 is only triggered once, and the access module 40 only conducts the NFC sensing module 20 and the control module 50 in a triggered state to trigger the control module 50; the control module 50 outputs a high level to the switch module 30 after being triggered to trigger the switch module 30; when the switching module 30 is in the triggered state, the NFC sensing module 20 and the NFC device 10 are turned on, so that the NFC device can be accessed by the NFC reader.
Further, referring to fig. 2, the NFC sensing module 20 includes an NFC antenna 201 and a switching circuit 202; the NFC antenna 201 is electrically connected to an ac input terminal of the switching circuit 202, a dc output terminal of the switching circuit 202 is electrically connected to a power input terminal (not shown in fig. 2) of the access module 40, a power input terminal (not shown in fig. 2) of the control module 50, and a power input terminal (not shown in fig. 2) of the switch module 30, respectively, and the NFC antenna 201 is further electrically connected to the switch module 30;
the NFC antenna 201 is configured to generate an alternating current output when the NFC device is close to an NFC reader; the conversion circuit 202 is configured to convert an ac output generated by the NFC antenna 201 into a dc output and output a dc voltage.
Specifically, when the NFC device is close to the NFC reader, the NFC antenna 201 generates an ac output, but the NFC antenna 201 and the NFC device 10 are not conducted because the switch module 30 is disposed between the NFC antenna 201 and the NFC device 10.
However, in order to meet the use requirement of the user, the conduction of the switch module 30 needs to be controlled. A direct current signal is more suitable for the control circuit than an alternating current signal, and therefore the conversion circuit 202 is arranged to convert the alternating current output generated by the NFC antenna 201 into a direct current output for the control of the switching module 30.
In addition, since the control module 50 and the switch module 30 both need to have the input of the working voltage to normally work, the dc output terminal of the converting circuit 202 is electrically connected to the power input terminal of the control module 50 and the power input terminal of the switch module 30, respectively, so as to provide the working voltage for the control module 50 and the switch module 30.
Still further, referring to fig. 3, the conversion circuit 202 includes a rectification circuit 2021 and a voltage stabilizing circuit 2022, the NFC antenna 201 is electrically connected to an ac input terminal of the rectification circuit 2021, a dc output terminal of the rectification circuit 2021 is electrically connected to the voltage stabilizing circuit 2022, and the voltage stabilizing circuit 2022 is electrically connected to the access module 40, a power input terminal (not shown in fig. 3) of the control module 50, and a power input terminal (not shown in fig. 3) of the switch module 30.
The rectifying circuit 2021 is configured to rectify an ac output generated by the NFC antenna 201 into a dc output; the voltage stabilizing circuit 2022 is used for limiting and stabilizing the dc output voltage of the rectifying circuit 2021.
Specifically, the ac output generated by the NFC antenna 201 is not necessarily stable, and therefore the dc output of the rectifier circuit 2021 is also unstable. Therefore, the dc output voltage of the rectifier circuit 2021 is limited and smoothed by the regulator circuit 2022, so as to improve the reliability of the NFC control circuit of the present embodiment.
In addition, one terminal of the rectifier circuit 2021 is commonly connected to one terminal of the regulator circuit 2022.
Still further, referring to fig. 3, the rectifier circuit 2021 includes a first rectifier diode D1, a second rectifier diode D2, a third rectifier diode D3 and a fourth rectifier diode D4.
Specifically, the anode of the first rectifying diode is electrically connected to the negative stage of the third rectifying diode to serve as a first pin of the ac input terminal of the rectifying circuit 2021; the anode of the second rectifying diode is electrically connected with the negative stage of the fourth rectifying diode to serve as a second pin of the alternating current input end of the rectifying circuit 2021;
the cathode of the first rectifying diode is electrically connected with the cathode of the second rectifying diode to be used as a first pin of the direct current output end of the rectifying circuit 2021; the anode of the third rectifying diode is electrically connected to the anode of the second rectifying diode to serve as a second pin of the dc output of the rectifying circuit 2021.
In the present embodiment, the diodes may be selected from the same type or different types of switching diodes or schottky diodes.
Still further, referring to fig. 3, the voltage regulator circuit 2022 includes a voltage regulator DW1 and a filter capacitor C1; the cathode of the voltage-stabilizing tube is electrically connected with the first pin of the filter capacitor, and the anode of the voltage-stabilizing tube is electrically connected with the second pin of the filter capacitor.
Specifically, the voltage regulator tube is used to limit the dc output voltage of the rectifier circuit 2021, and the filter capacitor is used to stabilize the dc output voltage of the rectifier circuit 2022.
Further, the access module 40 includes an access key, and the access key is electrically connected to the NFC sensing module 20 and the control module 50 respectively; specifically, when the access key is in a pressed state, the NFC sensing module 20 and the control module 50 are turned on to trigger the control module 50.
Specifically, when a user needs to use the NFC device, if the user needs to continuously press the key for use, the user experience is poor, and an access failure may be caused if the key shakes during the pressing process; if the user presses the key (or dials the key) and then the key remains in the pressed state (or dialed state), although the user can perform the operation, the user may easily forget to restore the key to the state before pressing (or before dialing) after the operation is completed, and thus the NFC device of the user may still be accessed by the NFC reader after being used.
Therefore, in this embodiment, when the user needs to use the NFC device, the user only needs to press the access key to complete the operation. After the operation is completed, the access button is in a disconnected state, so that the NFC read-write device cannot access the NFC device. Therefore, the user experience is good, and the safety is extremely high.
Further, referring to fig. 4, the switch module 30 includes an rf switch 301, and the rf switch 301 includes a power input pin (not shown in fig. 4), a ground pin (GND), a control pin (CTRL), a first switch pin (S1), and a second switch pin (S2).
A power input pin of the radio frequency switch 301 is electrically connected to the NFC sensing module 20, and a ground pin is grounded, so that the NFC sensing module 20 provides a working voltage for the radio frequency switch 301.
A control pin of the radio frequency switch 301 is electrically connected to the control module 50, a first switch pin of the radio frequency switch 301 is electrically connected to the NFC sensing module 20, and a second switch pin of the radio frequency switch 301 is electrically connected to the NFC device 10.
The radio frequency switch 301 is configured to conduct an electrical connection between the first switch pin and the second switch pin when the control pin has a high level input.
Specifically, when a high-level signal is input to the control pin of the radio frequency switch 301, two switch pins of the radio frequency switch 301 are turned on, so that the NFC sensing module 20 and the NFC device 10 form an electrical connection therebetween, and the NFC device can be accessed by the NFC reader.
In this embodiment, the rf switch 301 is SKY13453-385LF manufactured by SKYWORKS corporation, but other switch chips with similar functions may be used.
Still further, referring to fig. 4, the switch module 30 further includes a pull-down resistor R1, a first pin of the pull-down resistor is electrically connected to the control pin of the rf switch 301, and a second pin of the pull-down resistor is grounded.
The pull-down resistor is configured to disconnect an electrical connection between the first switch pin and the second switch pin when the NFC sensing module 20 just generates the dc output, so as to disconnect the NFC sensing module 20 from the NFC device 10.
Specifically, in order to ensure that the NFC sensing module 20 and the NFC device 10 can be reliably disconnected when the switch module 30 is just powered on (i.e., when the NFC sensing module generates an output), the pull-down resistor is arranged in series between the control pin and the ground, so that it can be ensured that there is no high-level input in the control pin when the switch module is just powered on, and therefore, the NFC sensing module 20 and the NFC device 10 can be ensured to be disconnected when the switch module is just powered on, thereby improving the reliability of the NFC access control circuit in this embodiment.
Further, referring to fig. 5, the control module 50 includes a first analog switch 501, and the first analog switch 501 includes a power input pin (VCC), a ground pin (GND), a control pin (CTRL), a switch pin (S), and an output pin (OUT).
A power input pin of the first analog switch 501 is electrically connected to the NFC sensing module 20, and a ground pin is grounded, so that the NFC sensing module 20 provides a working voltage for the first analog switch 501.
The control pin of the first analog switch 501 is electrically connected to the access module 40, the switch pin is electrically connected to the power input pin, and the output pin is electrically connected to the switch module 30.
Specifically, the first analog switch 501 is configured to turn on a switch pin and an output pin when a high level input exists at a control pin, so that the first analog switch 501 outputs a high level signal to the switch module 30.
Still further, the control module 50 further includes a second analog switch 502, where the second analog switch 502 includes a power input pin (VCC), a ground pin (GND), a control pin (CTRL), a switch pin (S), and an output pin (OUT).
A power input pin of the second analog switch 502 is electrically connected to the NFC sensing module 20, and a ground pin is grounded, so that the NFC sensing module 20 provides a working voltage for the second analog switch 502.
A control pin of the second analog switch 502 is electrically connected to the access module 40, a switch pin is electrically connected to a power input pin, and an output pin is electrically connected to the control pin and the control pin of the first analog switch 501, respectively.
Specifically, the second analog switch 502 is configured to turn on a switch pin and an output pin when the control module 50 is triggered and a working voltage is input, and output a high-level signal to the control pin and the control pin of the first analog switch 501 through the output pin at the same time, so as to maintain conduction between the switch pin and the output pin of the second analog switch 502 and maintain conduction between the switch pin and the output pin of the first analog switch 501.
In this embodiment, the user only needs to press the access module 40 (access key) to use the NFC device, but the time that the access module 40 is in the trigger state (i.e. the access key is in the pressed state) is very short, so that the first analog switch 501 and the second analog switch 502 are provided for successfully completing the entire operation, and are used for simulating the state when the access key is pressed, and the specific implementation process is as follows:
(1) when a user presses an access key, the NFC sensing module 20 outputs a high level signal to the control pins of the two analog switches at the same time, the switch pins and the output pins of the two analog switches are respectively turned on at the same time, and the output pins of the two analog switches can both output the high level signal at the same time because the switch pins are connected with the power input pins.
(2) Since the time for the access key to be in the pressed state is very short, the NFC sensing module 20 does not output a high level signal to the control pins of the two analog switches at the same time very soon, and therefore the output pin of the second analog switch 502 is electrically connected to the control pin thereof. In this way, even if the control pins of the two analog switches lose the high level input from the NFC sensing module 20, as long as there is an input of the operating voltage (i.e., the NFC sensing module 20 still generates an output), the output pin of the second analog switch 502 will continue to output the high level input to the two control pins at the same time, and further continue to keep the switch pins and the output pins of the two analog switches turned on, so that the output pin of the first analog switch 501 continues to output the high level signal to the control pin of the switch module 30. As such, the NFC device may be accessed by the NFC reader.
(3) When the user finishes the operation and the NFC sensing module 20 does not generate output any more, the output pins of the two analog switches cannot output high level signals any more because the two analog switches lose the working voltage, so as to disconnect the NFC sensing module 20 and the NFC device 10.
It is to be understood that the control module 50 is triggered after the access key is pressed, and continues to output a high level signal to the switching module 30 as long as the operating voltage is input. Therefore, when the user needs to operate, the user only needs to press the access key, and the method is very convenient.
Further, referring to fig. 6, the NFC access control circuit in this embodiment further includes a power-off delay module 60, a first pin of the power-off delay module 60 is electrically connected to the access module 40 and the control module 50, and a second pin is grounded; the power-off delay module 60 is configured to obtain and store power from the NFC sensing module 20 when the access module 40 is triggered, and provide a high-level input for a predetermined time to the control module 50 when the NFC sensing module 20 cannot output a normal voltage.
Still further, referring to fig. 6, the power-off delay module 60 includes a delay capacitor C2 and a delay resistor R1; the first pin of the delay capacitor is electrically connected with the first pin of the delay resistor to be used as the first pin of the power-off delay module 60; the second pin of the delay capacitor is electrically connected to the second pin of the delay resistor to serve as the second pin of the power-off delay module 60.
Specifically, the NFC sensing module 20 inevitably generates a discontinuous dc output due to instability, in which case it cannot be guaranteed that the control module 50 can always simulate the triggered state of the access module 40, and the access operation fails. Therefore, in order to improve the reliability of the NFC access control circuit, when the output of the NFC sensing module 20 is unstable, the delay capacitor is discharged through the delay resistor to output a high-level signal of a predetermined time to the control module 50, thereby ensuring smooth access operation and improving reliability. Specifically, the output time is related to the delay capacitor and the delay resistor. For example, assuming that the predetermined time t is 3 seconds, the delay capacitor and the delay resistor may be calculated according to the formula RC ═ t/ln (V0/Vt), where V0 is an initial voltage value of the delay capacitor, Vt is a voltage value of the delay capacitor at time t, Vt is set to 2.4V assuming that the minimum high level signal input of the first or second analog switch 502 is 2.4V, and RC ═ 4.09 assuming that V0 is 5V, and the delay resistor is about 4.7M Ω if the delay capacitor is selected to be 1 uF.
In addition, because the power-off delay module 60 is provided, when the user finishes the operation and the NFC sensing module 20 does not generate an output any more, the power-off delay module 60 also outputs a high-level signal for a predetermined time, that is, the NFC sensing module 20 and the NFC device 10 are still turned on within the predetermined time.
In summary, the NFC access control circuit provided in this embodiment includes an NFC device 10, an NFC sensing module 20, a switch module 30, an access module 40, and a control module 50. When the user does not need to use the NFC device, the NFC sensing module 20 and the NFC device 10 are disconnected because the switch module 30 has no high-level input, and the NFC reader cannot access the NFC device. When a user needs to use the NFC apparatus, the control module 50 outputs a high-level signal to the switch module 30 by only triggering the access module 40, so as to turn on the NFC sensing module 20 and the NFC device 10, thereby enabling the NFC apparatus to be accessed. In addition, after the user operation is completed and the NFC device leaves the NFC reader, the control module 50 does not output a high level signal to the switch module 30 any more, so that the NFC sensing module 20 and the NFC device 10 are disconnected, and thus the NFC device 10 cannot be accessed. It can be seen that, the NFC access control circuit provided by this embodiment is not only extremely convenient to operate, but also does not have potential safety hazards.
Based on the same inventive concept, another embodiment of the present invention provides an NFC device, which includes the NFC access control circuit as described above, and when the NFC device is close to an NFC reader, the NFC device is controlled by the NFC access control circuit to be accessible to the NFC reader.
Since the present embodiment and the above embodiments are based on the same inventive concept, specific implementations thereof can be found in the foregoing embodiments, and repeated descriptions thereof are omitted.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (12)

  1. The NFC access control circuit is applied to an NFC device and is characterized by comprising NFC equipment, an NFC induction module, a switch module, an access module and a control module;
    the NFC induction module is electrically connected with the switch module, and the switch module is electrically connected with the NFC equipment; the NFC induction module is also electrically connected with the access module, the access module is electrically connected with the control module, and the control module is electrically connected with the switch module;
    the NFC induction module is used for generating induction current and outputting direct-current voltage when the NFC device approaches the NFC read-write device;
    the access module is used for conducting the NFC induction module and the control module only in a trigger state so as to trigger the control module;
    the control module is used for outputting a high-level signal to the switch module after being triggered so as to trigger the switch module;
    the switch module is used for conducting the NFC induction module and the NFC equipment when being triggered, so that the NFC device can be accessed by an NFC read-write device.
  2. 2. The NFC access control circuit of claim 1, wherein the NFC sensing module comprises an NFC antenna and a switching circuit, the NFC antenna is electrically connected to an AC input of the switching circuit, a DC output of the switching circuit is electrically connected to the access module, a power input of the control module and a power input of the switch module, respectively, and the NFC antenna is further electrically connected to the switch module;
    the NFC antenna is used for generating alternating current output when the NFC device approaches the NFC read-write device; the conversion circuit is used for converting alternating current output generated by the NFC antenna into direct current and outputting direct current voltage.
  3. 3. The NFC access control circuit of claim 2, wherein the conversion circuit comprises a rectifier circuit and a regulator circuit, the NFC antenna is electrically connected to an AC input of the rectifier circuit, a DC output of the rectifier circuit is electrically connected to the regulator circuit, and the regulator circuit is electrically connected to the access module, a power input of the control module, and a power input of the switch module;
    the rectification circuit is used for rectifying alternating current output generated by the NFC antenna into direct current output; the voltage stabilizing circuit is used for limiting and stabilizing the direct current output voltage of the rectifying circuit;
    the rectifying circuit comprises a first rectifying diode, a second rectifying diode, a third rectifying diode and a fourth rectifying diode;
    the positive electrode of the first rectifying diode is electrically connected with the negative electrode of the third rectifying diode so as to be used as a first pin of the alternating current input end of the rectifying circuit;
    the positive electrode of the second rectifying diode is electrically connected with the negative electrode of the fourth rectifying diode so as to be used as a second pin of the alternating current input end of the rectifying circuit;
    the negative electrode of the first rectifying diode is electrically connected with the negative electrode of the second rectifying diode to be used as a first pin of the direct current output end of the rectifying circuit;
    and the anode of the third rectifying diode is electrically connected with the anode of the second rectifying diode so as to be used as a second pin of the direct current output end of the rectifying circuit.
  4. 4. The NFC access control circuit of claim 3, wherein the voltage regulator circuit includes a voltage regulator tube and a filter capacitor; the cathode of the voltage-stabilizing tube is electrically connected with the first pin of the filter capacitor, and the anode of the voltage-stabilizing tube is electrically connected with the second pin of the filter capacitor;
    the voltage-stabilizing tube is used for limiting the direct-current output voltage of the rectifying circuit, and the filter capacitor is used for stabilizing the direct-current output voltage of the rectifying circuit.
  5. 5. The NFC access control circuit of claim 1, wherein the access module includes an access button, the access button being electrically connected to the NFC sensing module and the control module, respectively;
    and when the access key is in a pressed state, the NFC induction module and the control module are conducted to trigger the control module.
  6. 6. The NFC access control circuit of claim 1, wherein the switch module comprises a radio frequency switch including a power input pin, a ground pin, a control pin, a first switch pin, and a second switch pin;
    a power supply input pin of the radio frequency switch is electrically connected with the NFC induction module, and a grounding pin is grounded so that the NFC induction module provides working voltage for the radio frequency switch;
    a control pin of the radio frequency switch is electrically connected with the control module, a first switch pin of the radio frequency switch is electrically connected with the NFC induction module, and a second switch pin of the radio frequency switch is electrically connected with the NFC equipment;
    the radio frequency switch is used for conducting electric connection between the first switch pin and the second switch pin when the control pin has high level input so as to conduct the NFC induction module and the NFC equipment.
  7. 7. The NFC access control circuit of claim 6, wherein the switch module further comprises a pull-down resistor, a first pin of the pull-down resistor is electrically connected to a control pin of the radio frequency switch, and a second pin of the pull-down resistor is grounded;
    the pull-down resistor is used for disconnecting the electric connection between the first switch pin and the second switch pin when the NFC induction module just generates direct current output so as to disconnect the connection between the NFC induction module and the NFC equipment.
  8. 8. The NFC access control circuit of claim 1, wherein the control module includes a first analog switch including a power input pin, a ground pin, a control pin, a switch pin, and an output pin;
    a power supply input pin of the first analog switch is electrically connected with the NFC induction module, and a grounding pin is grounded so that the NFC induction module provides working voltage for the first analog switch;
    a control pin of the first analog switch is electrically connected with the access module, a switch pin is electrically connected with a power input pin, and an output pin is electrically connected with the switch module;
    the first analog switch is used for conducting a switch pin and an output pin when a high level input exists at a control pin, so that the first analog switch outputs a high level signal to the switch module.
  9. 9. The NFC access control circuit of claim 8, wherein the control module further comprises a second analog switch comprising a power input pin, a ground pin, a control pin, a switch pin, and an output pin;
    a power supply input pin of the second analog switch is electrically connected with the NFC induction module, and a grounding pin is grounded so that the NFC induction module provides working voltage for the second analog switch;
    a control pin of the second analog switch is electrically connected with the access module, a switch pin is electrically connected with a power input pin, and an output pin is electrically connected with the control pin and the control pin of the first analog switch respectively;
    the second analog switch is used for conducting a switch pin and an output pin when the control module is triggered and working voltage input exists, and outputting high-level signals to the control pin and the control pin of the first analog switch through the output pin simultaneously so as to keep conduction between the switch pin and the output pin of the second analog switch and keep conduction between the switch pin and the output pin of the first analog switch.
  10. 10. The NFC access control circuit of claim 1, further comprising a power-off delay module, wherein a first pin of the power-off delay module is electrically connected to the access module and the control module, and a second pin of the power-off delay module is grounded;
    the power-off delay module is used for getting and storing power from the NFC induction module when the access module is triggered, and providing high-level input of preset time for the control module when the NFC induction module cannot output normal voltage.
  11. 11. The NFC access control circuit of claim 10, wherein the power-down delay module comprises a delay capacitor and a delay resistor;
    the first pin of the delay capacitor is electrically connected with the first pin of the delay resistor to be used as the first pin of the power-off delay module;
    and the second pin of the delay capacitor is electrically connected with the second pin of the delay resistor so as to be used as the second pin of the power-off delay module.
  12. 12. An NFC device comprising an NFC access control circuit according to any one of claims 1 to 11, wherein the NFC device is controlled by the NFC access control circuit to be accessible to an NFC reader when the NFC device is close to the NFC reader.
CN202010001257.4A 2020-01-02 2020-01-02 NFC access control circuit and NFC device Active CN113067604B (en)

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PCT/CN2020/131559 WO2021135741A1 (en) 2020-01-02 2020-11-25 Nfc access control circuit and nfc apparatus

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CN107547470A (en) * 2016-06-24 2018-01-05 中兴通讯股份有限公司 Mobile terminal and NFC pay control method
CN107911147A (en) * 2017-11-10 2018-04-13 深圳市文鼎创数据科技有限公司 A kind of control circuit and smart card for NFC near-field communications
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